1. Field of the Invention
The present invention relates to hemostatic materials incorporating various structures, such as nanostructures. The invention further relates to highly absorbent scaffold materials with hemostatic materials incorporated therein. The present invention further relates to materials incorporating nanostructures for enhanced platelet binding.
2. Background of the Invention
Coagulation is a process by which blood forms solid clots. Coagulation is an important part of hemostasis (the process of halting blood flow). During natural hemostasis, a damaged blood vessel wall is covered by a platelet- and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel. Various materials, referred to as “hemostats” or “hemostatic materials,” have been developed to help stop wounds from bleeding excessively and to increase a rate of clotting. Such materials may be used in surgical procedures and/or by first responders to traumatic events, for example.
Some hemostatic materials that have been developed are bandage based, including oxidized resorbable cellulose materials, or cotton gauze sponges used to pack wounds prior to the application of pressure. Such bandage based materials are typically not inherently hemostatic, functioning more as absorbers of blood and leading to a plugging of a wound. Products are available that increase the hemostatic activity of a bandage material by incorporating biological agents of the natural physiological clotting cascade, such as thrombin. Such products suffer from cost and stability issues that limit their use. Thus, a need exists to increase the rate of hemostasis on bandage materials, while eliminating the conventional problems of high cost and instability.
Some bulk hemostatic materials exist that are poured into a wound to clot blood, such as QuikClot®, distributed by Z-Medica Corporation, Wallingford, Conn. Such bulk hemostats have disadvantages. For example, such existing bulk hemostats do not function as quickly as desired, may be difficult to apply, and not all existing bulk hemostats can be absorbed by the human body. Furthermore, existing bulk hemostats have an exothermic reaction with blood. Thus, a need exists for bulk hemostatic materials that overcome at least some of these disadvantages.
Biocompatible polymers have also been used as hemostats. For example, resorbable expandable polymers have been used for wound closure to prevent blood loss after endoscopic surgery where the entry/exit point of the endoscopic device is through a blood vessel. An example such device is the Angioseal™ vascular closure device sold by St. Jude Medical, St. Paul, Minn. Absorbent materials, such as cotton gauze or tampon structures, have also been used for wound closure. In a device using an expandable material, blood and/or other fluids are absorbed by the material, and the material swells to cause a physical barrier. Static blood may be entrapped within pores of the material, and the entrapped blood subsequently clots due to stasis. It would be advantageous if the blood within the expanded material could be made to clot more rapidly. One possibility for increasing a rate of clotting is a biological technique using clotting enzymes. However, such a technique would be expensive. A need exists for expandable and/or absorbent material-based devices that have improved rates of clotting, while keeping down device costs.
Current methods of hemostasis, including most surface-based enhancers of coagulation such as zeolite or kaolin clays, trigger coagulation by two mechanisms: (1) providing a surface for activation of the contact (intrinsic) coagulation cascade, and (2) adsorbing water from the blood, thereby concentrating the components of the coagulation cascade at the provided surface. However, such a method of inducing hemostasis is not typical of the physiologically relevant response whereby an activated surface triggers the intrinsic coagulation pathway and also leads to enhanced platelet binding. Thus, there exists a need to provide hemostatic methods and devices which will trigger the intrinsic coagulation pathway and enhance platelet binding to increase the rate of hemostasis.
Inorganic materials have been used as hemostats in various forms. For example, zeolite clays have been used to induce hemostasis. However, these approaches suffer from certain drawbacks such as poor absorptivity of the scaffold material to which they are applied. Thus, there exists a need for a highly absorbent scaffold for the incorporation of hemostatic materials such as inorganic nanostructures. Further, there is a need for a highly absorbent scaffold that will allow larger volumes of blood to be exposed to hemostatic particles incorporated therein.